It's most impressive trait is that it is a holistic approach to UI and design. There aren't many "systems" out there for that.
However I agree, there isn't much new and impressive in it and the evangelistic design chatter it created, much like the Flat Design trend, gets very stale and can stifle good conversation on the topic.
What's sad is that people see it as an endpoint. While the thing is obviously meant to be a starting point, a baseline of "good design" that you can expand on if you wish, or stick to if you have better things to do.
It moves the baseline from zero design to "good" .
Which was the great thing about flat design too. It brought basic good design principles to the discussion. Whether you liked the asthetic or not, the core guiding principles were the real win.
I feel like the creators of the Material Design site simply sought to formalize those principles and build upon them, which I think they have done a good job of.
However I agree, there isn't much new and impressive in it and the evangelistic design chatter it created, much like the Flat Design trend, gets very stale and can stifle good conversation on the topic.